Recently, the understanding of metabolic reprogramming in cancer is expanding continuously.Besides glycolysis, researchers are now paying more attention to amino acid metabolism, especially glutamine metabolism.Glutamine is one of the most abundant non-essential amino acids in human body, but it is a “conditionally essential” amino acid in various types of cancer cells.Thus, targeting glutamine metabolism is becoming a promising strategy for the development of novel cancer therapeutic agents.In addition, another gradually clarified metabolic pathway is serine and glycine metabolism.In this review, we will focus on the alterations, the underlying mechanisms, and significance of glutamine as well as serine and glycine metabolism.We will also discuss cancer therapy opportunities through targeting amino acid metabolism.